Performance of low-cost fiber optic cables as leak detection sensors for water pipelines in unsaturated soil

Abstract

Large volumes of potable water are lost from leaks in water distribution systems around the world. Such leaks may go undetected for a long time. A passive means of leak detection can be implemented by burying a suitable fiber optic cable in the pipe trench with water distribution pipes when they are installed. Water leaking from pipes into the ground results in a temperature change at the leak location. Leaks into unsaturated soil also cause changes in the bulk density and strength of the soil, resulting in significant soil deformation. Brillouin Frequency Shift (BFS) in optical fibers is sensitive to changes in both temperature and mechanical strain, allowing fiber optic cables to act as efficient leak detection sensors. Purpose-made fiber optic cables may be expensive, but telecommunication grade cables generally have a low cost and are readily available around the world. This paper investigates the performance of five different fiber optic cables, including communication grade fiber optic cables, to act as leak detection sensors in unsaturated ground. It was found that the most efficient leak detection sensors are flexible tight-buffered fiber optic cables.